Batteries that comprise liquid electrolyte, such as lead acid batteries or the like used in deep cycle or other applications, require for optimum performance that the liquid electrolyte contained within each electrolytic cell be maintained at a specific electrolyte level. The desired electrolyte level generally corresponds to the volume of electrolyte that is needed to completely submerge the battery electrode plates contained within the electrolytic cell. Completely submerging the electrode plates of the battery with electrolyte promotes optimal battery operation, as it provides a maximum degree of electrolyte to electrode plate contact, and thereby promotes a maximum degree of electricity generating electrochemical reaction within each electrolytic cell of the battery.
To maintain an optimal level of battery performance, and to maximize battery service life, the battery electrolyte level must be checked regularly and replenished in the event that it is below a desired level. The electrolyte level in the electrolytic cells of a battery is not static, but is dynamic due to the effects of evaporation, leakage or spillage, and due to outgassing that occurs during overcharge in the charging process. To obtain maximum results during battery charging it is desired that the battery electrolyte level be checked and adjusted during and after the charging operation, to thereby ensure a maximum degree of electrolyte to electrode interface during the charging process.
An electrolyte battery typically comprises a number of electrolytic cells. For example, a conventional 12 volt electrolyte battery comprises six two-volt electrolytic cells. Different battery applications call for different overall battery voltages and, therefore, different battery configurations. Such battery applications typically require that the battery be stored onboard the battery-powered device or vehicle at a location that does not always permit easy access to each electrolytic cell, making electrolyte level inspection and electrolyte replenishment difficult and time consuming.
Devices have been constructed in an attempt to address such difficulties associated with electrolyte level checking and electrolyte replenishing in such applications. To reduce or eliminate the risk of environmental hazard or health danger during the electrolyte replenishment operation, it is desired that only water be used or circulated to fill the electrolytic cells.
Devices known in the art that have been developed to facilitate electrolyte leveling and replenishment include so called "pass-through" devices that are adapted for installation into each electrolytic cell of the battery. Such pass-through devices typically include an inlet port and an outlet port that are positioned within the cell to permit flow-through passage of electrolyte from the cell when a determined electrolyte level in that cell is achieved. The pass-through devices are installed into each electrolytic cell of the battery and are hydraulically connected together to permit the serial circulation of electrolyte through each electrolytic cell, filling each cell to a determined electrolyte level, and finally out of the battery for collection.
Electrolyte replenishment or filling is accomplished using such a pass-through device by routing water from a water source to a first device, that is disposed in a first electrolytic cell, until the electrolyte level reaches a determined level. While water addition to the first filled cell is continued, water mixed with electrolyte from the filled cell is routed through its respective device to another device that is installed in a different cell. This chain of electrolyte transfer continues until the determined electrolyte level in a final battery cell is achieved and electrolyte is routed away from the battery and the water flow is discontinued.
A disadvantage of the pass-through device is that it requires electrolyte, rather than only water, to be transferred through the electrolytic cells and eventually away from the battery, where it can pose an environmental or health risk. Additionally, when connected in series with a number of other such devices, the device is unable to provide a desired concentration of electrolyte in each cell. Rather, as mixed water and electrolyte is circulated through each cell the electrolyte concentration in each cell become progressively more diluted than the next cell in the series, thereby causing the electrolyte concentration in each cell to vary.
Another device designed to facilitate electrolyte leveling and replenishment is a mechanical "float-type" device that is configured to fit into an electrolyte fill opening of an electrolytic cell. The device comprises a body that is engaged into the fill opening. A plunger extends from the body into the cell and includes a float that is designed to float in the electrolyte. The body includes a valve mechanism which is located outside of the electrolytic cell and is designed to open and close the flow of water through a water inlet in the body to the cell, depending on the position of the plunger and float.
When the electrolyte level in a cell is low, and the plunger and float extend downwardly into the cell a determined distance, the valve in the body is opened to permit water flow into the cell. Once a desired electrolyte level is achieved, and the plunger and float rises in the cell to a determined point, the valve is closed, causing water flow to the cell to cease. The device also includes a vent passage in the body that allows air being displaced by the water entering the cell to be routed from the cell through the body and to the atmosphere. These devices, when installed in respective cells, are hydraulically connected to a water source in parallel so that as the electrolyte level in each particular cell is achieved the water flow to that cell is shut off.
Embodiments of the above-described float-type device are designed to permit the filling of more than one electrolytic cell from a single location. In such an embodiment, each device additionally comprises a water outlet that permits the passage of water through its body either during or after the determined electrolyte level, for the particular cell within which the device is installed, is achieved. The device is placed into each electrolytic cell and is hydraulically connected, with piping or tubing and the like, to permit electrolyte filling of each cell with water from a single point. The use of such device allows the electrolyte level in each cell to be replenished without circulating electrolyte between cells and away from the battery.
Although such a device permits circulation of water from a water source through each device without allowing electrolyte to leave the battery, it does so using mechanically moving parts, e.g., the plunger and valve arrangement. The use of a device having moving parts in an electrolyte battery cell service is not desired because of the likelihood that such mechanism will fail, or its operation will become impaired or unpredictable, due to its exposure to the highly corrosive environment of the electrolytic cell, e.g., its exposure to sulfuric acid, sulfuric acid vapors and the like. Sulfuric acid vapors, nascent oxygen, and hydrogen produced during operation or charging of the battery are allowed to escape from each cell via a passage through the device body, thereby placing the moving parts in direct exposure to such corrosive and highly aggressive vapors. It is known that prolonged exposure to such vapors eventually reduces the operating life of the device due to part failure.
Additionally, plastics and rubbers that are used in conjunction with the device and/or device-to-cell seal are known to decompose after being exposed to such corrosive liquid and/or vapor. The products of such decomposing material enter the device and are known to interfere with the movement of the parts, e.g., causing the valve to stick in an open or closed position and, thereby rendering the device inoperative. Additionally, the decomposition products of such plastic and rubber parts are known to enter the electrolytic cell, interfering with the efficiency of electrochemical reaction occurring therein.
U.S. Pat. No. 4,754,777 discloses another device for replenishing the electrolyte level in electrolyte battery cells. The device comprises a body that fitted into the fill opening of an electrolytic cell. The body has no moving parts, but provides water flow into the cell from a water inlet via a water trap arrangement. The water trap is designed so that water from the water inlet is directed through the trap at a particular supply pressure and into the electrolytic cell. The water flow through the trap and into the cell terminates when the pressure of air trapped within the device equals the water supply pressure, causing the supply water to bypass the trap and be routed from the device via a water outlet to the next serially connected such device an another battery cell.
The water pressure inside the trap when water flow through the trap ceases is related to the water supply pressure, which is regulated by a pressure control valve installed between a water inlet of the device and a water source. Because the shut-off water pressure in the trap is a function of the inlet water pressure, the electrolyte level that is provided by the device is pressure sensitive, i.e., the electrolyte level in each electrolytic cell varies depending on the inlet water pressure that the device sees. For this reason it is necessary that the pressure control valve be used to fix the inlet water pressure to a desired constant value that provides a desired electrolyte level.
U.K. Patent No. 1,041,629 discloses another "trap-type" device that is very similar to the trap-type device described above, in that the device makes use of a water trap to control the dispensement of water into an electrolytic cell. The device operates using the same principles of operation as the other trap-type device and is constructed to provide an electrolyte level within the cell that is sensitive to the water supply pressure.
The above-described trap-type devices are adapted to be hydraulically connected in series with identical such devices that are installed in other electrolytic cells to provide serial battery leveling and replenishment. However, because the inlet water pressure to each device determines electrolyte level in each cell, the pressure losses that occur through the series arrangement of devices can cause the electrolyte level to be progressively lower in each sequentially arranged cell, making accurate electrolyte leveling in each cell difficult. Additionally, such trap-type devices are constructed so that once the desired cell electrolyte level is achieved, and gas that is produced within the cell is prohibited from exiting the cell, thereby creating a potential explosion hazard.
Although the above-described trap-type devices do permit electrolyte leveling and replenishment without circulating electrolyte between electrolytic cells and away from the battery, and without the use of moving parts, the ability of such devices to do so is dependent on the inlet pressure of the water, thereby making such devices unsuited for use in applications where precise water pressure regulation is not available and/or practical.
Additionally, the described trap-type devices are not capable of operating under vacuum conditions, e.g., where a differential pressure through the device is created under vacuum rather that positive pressure operating conditions. The ability to perform electrolyte leveling and replenishment using a vacuum induced differential pressure through the device is desirable because it eliminates the possibility of water leakage occurring outside of the battery, which may be caused by leaking connection tubing or the like.
It is seen, therefore, that a need exists for a device which has some of the following characteristics: it permits electrolyte leveling and electrolyte replenishment for electrolytic cells of an electrolyte battery from a single point, i.e., from a single connection point with a water source; it is capable of both replenishing an electrolytic cell with water to a determined electrolyte level and circulating water, not electrolyte, through the device to one or more other devices that are installed in respective cells once its own cell is filled; it has no moving parts and can provide electrolyte leveling and replenishment independent of variations in the differential pressure within the device; and it can be used in either positive pressure or vacuum operating conditions.